The invention concerns a method and apparatus for grinding that employs a coolant fluid. In particular, it relates to an enhancement to a process called creep-feed grinding by means of which a very high stock removal rate is achieved.
Creep-feed grinding is a full depth or full cut operation that often allows a complete profile depth to be cut from a solid in a single pass. The workpiece to be machined is fixed to a surface table which is fed passed the rotating grinding wheel at a constant speed. The stock removal rate is set by the size and number of chip cavities in the surface of the wheel in combination with a number of other factors. A high removal rate can be achieved, but the process can generate sufficient frictional heat to burn the workpiece surface and damage the wheel. Increasing the depth of wheel cut hitherto had required reduced workpiece feed rate or performing the operation in two or more passes.
Improvements have been found by providing adequate coolant flow to the wheel contact region ensuring workpiece cooling and grinding wheel cooling and efficient cleaning. It is well known to use jet cleaning nozzles delivering coolant close to the wheel surface in large volumes. The type and composition of the wheel is carefully chosen for the type of material to be ground for the most acceptable balance between stock removal rate and wheel wear.
Removal of metal material from a workpiece at higher rates can require a significant quantity of coolant that must be delivered precisely and in sufficient quantities at, and across the entire profile of, the interface between the metal working tool and the workpiece. Typically, the coolant nozzle is positioned manually by an operator based on experience and an estimate of an orientation and position that will deliver the coolant stream at the metalworking tool. The significant volume and pressure of the stream of coolant during a grinding operation, for example, floods the grinding compartment and obscures any view of the exact position of the coolant stream's impact and of the machining interface. Often, if the coolant stream has not been precisely delivered to the machining interface, the machined workpiece will have flaws due to excessive heat buildup or material removal, and must be reworked or scrapped.
Therefore, further improvements are needed to ensure that an adequate stream of coolant is delivered precisely and in sufficient quantities across the profile of the machining interface between the metalworking tool and the workpiece.